The present invention relates to a sector pulse generating apparatus for a disk memory, and more particularly to a sector pulse generating apparatus for multiple zone recording of a disk memory.
A "disk memory" refers to a disk-type recording medium such as a hard disk, a flexible disk, and an optical disk. A typical disk memory has a plurality of circular tracks. Each track includes a plurality of sectors having an arc-like shape.
A "sector length" of a sector refers to an angle between segments OA and OB, where points O, A, and B are the center of the disk memory, an endpoint of the sector, and the second endpoint of the sector, respectively.
A "maximum sector number" refers to the number of sectors included in a track.
A "zone" refers to a region of the disk memory in which all tracks include the same number of sectors. All tracks in a zone have the same maximum sector number. All sectors in a zone have the same sector length.
"Multiple zone recording" refers to data recording or reproducing in which a plurality of zones having different maximum sector numbers are provided in the disk memory.
A "large zone" and a "small zone" refer to first and second zones, respectively, where the maximum sector number of the first zone is greater than that of the second zone.
An "index signal" refers to a signal indicating that the disk memory is in a predetermined position relative to a recording/reproducing head. In a typical flexible disk drive, the index signal is generated by detecting an index hole provided in the flexible disk. In a typical hard disk drive, the index signal is generated by reproducing and converting information recorded in the hard disk.
In a disk memory drive, sector pulses are generated for synchronization of data recording or reproducing.
The sector pulses occur at a regular time interval. Thus, the sector pulses can be generated by counting reference clock pulses and outputting the sector pulses every Np clock pulses. Hereinafter, the number Np is referred to as a "sector length" of a sector because Np is directly proportional to the sector length of the sector defined above.
In multiple zone recording, the reference clock counter is reset when the head is moved across a zone boundary because the sector length Np varies from zone to zone. The reference clock counter starts counting again when it receives an index signal. Thereafter, the counter operates in the same way with respect to a new sector length Np Thus, the generation of the sector pulse is deferred until the index signal arrives.
A conventional sector pulse generating apparatus for eliminating the aforementioned delay in sector pulse production is disclosed in Japanese Laid-Open Patent Publication Hei 4-125859 (1992).
Referring to FIG. 1, the conventional apparatus comprises first to n-th sector pulse generating circuits 43-1 to 43-n corresponding to first to n-th zones, respectively. The sector pulse generating circuit 43-i outputs sector pulses every Np-i reference clocks, where Np-i is the sector length of the i-th zone. Thus, the sector pulse generating circuit 43-1 to 43-n simultaneously generate the sector pulses 48-1 to 48-n of first to n-th zones, respectively.
The conventional apparatus also comprises first to n-th sector pulse counters 44-1 to 44-n counting the sector pulses 48-1 to 48-n, respectively. The count value of the sector pulse counters 44-1 to 44-n are output as signals 49-1 to 49-n, respectively. The sector pulse counters 48-1 to 48-n are reset when they receive an index signal 102.
The conventional apparatus further comprises a multiplexer 45. According to zone select signals 42-1 to 42-n indicating one of the zones, the multiplexer 45 selects one of the sector pulses 48-1 to 48-n and a corresponding one of the signals 49-1 to 49-n. The selected sector pulse and signal are output as a sector pulse signal 106 and a sector pulse count value 47.
In this apparatus, when the head is moved across a zone boundary, new sector pulses are generated immediately without waiting for the arrival of the index signal because the sector pulse generating circuits 43-1 to 43-n generate sector pulses of all zones simultaneously.
However, this apparatus needs the same number of sector pulse generating circuits as the number of zones in the disk memory. Therefore, as the number of zones increases, the size and the complexity of the apparatus increases.